Machine for metering cement to lenses



WE1? E I 'I JW Zemuhgoa E 'Y Sept. 3, 1946. jw. T. sH'gR/vn 2,407,208

" MACHINE FOR METER'EG- CEMENT To LENSES J l .f v 4 Fiied Maren '7, 1945 WILLIAM T. SHERWO OD INVENTOR W24/fm Y BY M25 Patented Sept. 3, y 1946 2,407,208 MACHINE FOR METERING CEMENT 'ro LENSES William T. Sherwood, Rochester, N. Y.`,va`ssignorn K Y l to Eastman Kodak Company, Rochester, N. Y., I Q

3 a corporation of New Jersey f 5 Claims.

'Ihis invention relates to machines for metering cement to be applied to lenses. One object of my invention is to provide a machine for metering exact quantities of cement to lenses to enable an operator to apply cement in such a manner that two lenses may be cemented together over their entire complementary-shapedurfaces without having any cement left to be pressed out between the edges of the lenses, and` later, removed therefrom. Another object of my invention is to provide a machine particularly designed for applying a thermo-plastic cement to lenses and to a machine for maintaining the cement and lens at the desired temperature. Still another object of my invention is to provide a machine with a cement .gdropper which is maintained at the required tem- Wperature to drop a quantity of cement upon a lens and to provide a means for varying the quantity of cement at will. Another object of my invention is to provide a machine which may be used with a thermo-setting as well as a thermoplastic cement. Other objects will appear from the following specification, the novel features being particularly pointed out in the claims at the end thereof. i f For a great many years Canada balsam has been used for cementing together lens elements used in making up an objective. This cement is entirely satisfactory for most purposes, but unfortunately it will not stand the extremes in temperature met with at high altitude, such as is necessary for photographic objectives .used in aerial cameras. It has been found that extreme cold will render Canada balsam useless as a cement and will prevent an objective utilizing this cement from producing satisfactory images. In a copending application in the name of Messrs. Thuline, Parsons and Waugh, Serial No. 490,082, filed June 8, 1943, for Thermo-plastic cement, a number of different cement formulas are given and these cements are found entirely satisfactory, withstanding both the extreme cold due to high altitude or the extreme heat which is met with in the tropics. Such cements are somewhat difficult to apply in a satisfactory manner to lenses. If a drop of such cement is placed on one lens and the lens to be cemented is applied in the usual manner and pressed upon the rst lens, difficulties are liable to be encountered in that air bubbles may be entrapped and it may be a long and diicult operation to remove the air bubbles and to thin out the layer of cement to the desired thickness. It is likewise diiiicult to properly center the lenses unless they are maintained at a fixed temperature. 1f tde much "Application March 7,1945, sena1N0.5s1,529

' cement is applied and is gradually worked out around the periphery of the lens as the lenses are centered, this cement must be later removed after v ithas become'set. This operation is a diicult one 5 to accomplish economically, and sometimes such cement prevents the lens from being properly centered in its mount unless all traces of the unwanted cement are removed. If too little cement is applied, the layer cannot be spread over the entire contacting surfacescf the lenses to be cemented and the operation must be repeated. -,I have provided a cement dropping machine so designed that accurately metered quantities of cement may be applied to one lens element so that form of my invention;

Fig. 2 is a top plan View of the mechanism for limiting the amount of cement delivered at each stroke of an operating handle; .v

Fig. 3 is a sectional view through a lens holder into which the cemented lens elements may be placed after the cement has been applied; Y Fig. 4 is a section through a typical cemented lens element and illustrating elements which can be supplied with cement by my machine; and

35 Fig. 5 is a fragmentary detail section on a greatly enlarged scale showing how the cement ows outwardly from the center to the edge of lenses being cemented together and indiating how the proper amount `of cement prevents an 4.0 unwanted spreadrof cement beyond the edges of the lenses., w 2., ,ufff-My cement metering machine consists broadly in a cylinder into which a plunger is automatically advanced a like amount each time an operating handle is moved. The cylinder is provided with a cement dropping nozzle and the movement of the plunger together with the shape of the nozzle definitely determines the exact amount of cement applied to a given lens. 50 My machine may consist of a base member preferably carrying a slide member 2 having three upstanding posts 3 for centering a lens L beneath the cement dropper. The slide 2 may carry posts 3 spaced the proper distance for the particular lens to be cemented and it may also carry a suitable heating element 4 connected by sockets 5 and plugs-6 to a source of power I. A rheostat 8 may be used for controlling the temperature of the heating element 4 and consequently that of the lens L.

A bracket G extends upwardly from the base I and may be provided with a pair of arms I and I I extending outwardly to support a heating element I2. This heating element surrounds a cylinder I3 and controls the temperature of the' cylinder and cement C carried thereby. On the bottom of the cylinder there is a nozzle I4 which may be attached by means of a thread I5 to the cylinder, this nozzle having an orifice I8 which assists in determining the size of a drop of cement which is delivered each time a plunger Il is lowered into the cylinder by a predetermined amount.

Around the orice i6 of the cylinder, I provide a heating element I8 which is connected through to the source of power 'l and which passes through a. rheestat I9 so that the temperature of this coil may be controlled. The reason for this coil is that a droplet D of cement issuing out of the orince l5 is liable to harden unless it is kept at the proper dropping temperature.

The heating element I2 is connected to the source of powel` 'l through a rheostat 2S. Thus, the three heating elements, I2, I8 and 4 may be separately controlled in order to control the exact amount of cement which is dropped at each operation of a handle 2 I.

This handle 2| carries a plunger 22 pressed by a spring 23 into engagement with ratchet teeth 24 on the nut 25 threaded at 28 to turn on the thread 2 carried by the plunger I l. The thread- .iied member 21 is held against turning by means of a pin 28 entering a key slot 29 in the threaded member. The pin 28 is carried on a screw 35 which may be moved to and from the slot 29 by mean-s of a handle 3 I. l

The handle 2| is carried by a disk 32 which is mounted to rotate between the annular member 33 and the collar 34, this collar being held in place by the cap member 35 by means of the screws 36.

A spring 3l having one end 33 anchored on the handle 2| and the other end 39 anchored on the bracket extension I I tends to hold the handle 2| in the position shown in Fig. 2 in which it rests against a stop 4U. However, the collar 34 can be adjusted so that an arm 4I extending radially therefrom can be positioned in different angular positions with respect to the stop 4D. This can be accomplished by means of the setscrew 42 as shown in Fig. 2. When it is desired to cement a particular size of lens L, one of these lenses is placed between the holding posts 3 and the cement C in the cylinder I3 is brought up to the proper temperature for that particular cement. This temperature may be in the neighborhood of 300. It is preferable to hold the lens L and the heating coil I8 at the same temperature, that is 300, although these temperatures may be varied at will by means of the rheostats 8, I9 and 20. The arm 2| is then advanced to move the nut 25 through a predetermined angle, thus lowering the plunger Il by a predetermined amount due to the threads 25 and 2l. This squeezes a droplet D out 0f the orifice IS and, if the proper quantity of cement is dropped upon the lens L, the lenses to be cemented can be joined by placing the lens L with its droplet D in a suitable holder such as the one shown in Fig, 3. A second lens L1 is then laid upon the rst lens L and upon the droplet D and this holder is placed in an oven. e oven should maintain the temperatures of the lenses and cement at the dropping temperature, as for instance 300, and it will be found that the capillary attraction of the cement and lens surfaces combined with the Weight of the lens L1 will cause the cement to gradually ow between the two lens elements until their surfaces have been entirely covered by the cement. As shown in Fig. 5, if exactly the right amount of cement has been i applied, the cement will ilow up to the peripheries P and P1 of the lenses L and L1, but it will not ow out over the edges. Thus if exactly the right amount of cement is furnished only the necessary amount is applied to provide a layer of between 10 and 2O microns of cement between the lenses and it will be unnecessary to clean any cement from the periphery of the lenses.

After the cement has properly spread between the lens elements they are gradually cooled, as by moving the lenses through an oven, gradually reducing the temperatures and, at least to some extent, annealing the lens elements. It will be found that when such a lens is cooled, as explained in the above-mentioned application, a

very permanent bond between the lenses will be formed which will withstand relatively high heat, such as 209 or more, and also extremely cold temperatures, such as -50 or -60. Such lenses are entirely suitable for aviation cameras.

3o It is quite possible to adjust the droplet D to the exact amount required forA any size of objective and, while this is usually done by trial and error, it can be calculated in advance quite closely. When the proper stroke for the handle 2l has been determined the stop 4I can be fastened in position by the screw 45. so that each time the handle is moved between the stops 4l! and 4I the correct amount of cement will be dropped through the orice IE. v j

I have found it desirable to provide a number of nozzles I4 similar to the one described above except for the size of the orince I6. It is ob viously desirable to provide smaller orifices when small lenses are to be used and, no doubt, one

l orifice may serve for a large number of different sizes of lenses. However, it is more convenient to provide several diiferent orillcesvwhich can be readily screwed to the bottom of the cement cylinder I3. Y

'50 While my cement dropper can be used satisfactorily with thermo setting as well as with thermo-plastic cements, it is primarily intended for use with thermo-plastic cement. It is, hov\- ever, important with any type of cement to be able to drop or meter out the exact quantity of cement required, because by so doing a second cleaning operation can be completely avoided. Moreover, it is desirable to furnish the exact quantity ci' cement for another reason. If the exact quantity is furnished for any two lenses to be cemented, the thickness of the cement layer between the two Vlen-ses can be accurately controlled and thus the corrections calculated for the particular lenses can be maintained regardless of the number of lenses manufactured. In other words, there will be no appreciable variation between two lenses having known optical characteristics because the cement layer may be accurately held to the de'l sircd thickness. When cementing lenses by hand,

and when cement is applied without metering, the two len-s elements must be carefully worked together by a skilled operator so that the lenses are brought into the proper relationship. gradually working out any air bubbles which may oc cur due to the spreading of the cement so that any excess cement passes out around the periphery of the lenses. After the lenses have been centered and set, this excess cement must be manually removed and this operation must be carefully performed in order to preserve the proper relationship between the lens elements and in order to remove all the cement from the peripheries P so that the lenses may be later mounted in their usual mounts.

With my improved dropper, by controlling the.

exact amount of cement deposited on each lens, the cleaning operation is unnecessary, the layer of cement can be maintained accurately at an accurate thickness and the hand centering of the lenses can be entirely omitted. Since the stroke of the plunger can be accurately controlled after the size oithe droplet D required for the particular work' at hand has been determined, repeated operations of the lever will cause each succeeding drop of cement issuing from the oriiice to be exactly the same as the preceding drop. Thus cement can be applied rapidly and accurately with the machine as above described.

While I have described a preferred embodiment of my cement dropper, it is obvious that various changes can readily be made in the details of construction thereof. I consider as within the scope of my invention all such forms as may come within the scope of the appended claims.

I claim:

1. A machine for applying metered quantities of cement to lenses comprising a support, a lens holder mounted thereon, a cement cylinder amounted above the lens holder, a plunger mov- Vably mounted in the cylinder, a pawl and ratchet for advancing the plunger into the cylinder by predetermined amounts, a coupling on the cylinder positioned over the lens holder, a nozzle having an orifice adapted to be attached to the coupling and to extend downwardly therefrom and over the lens holder, said plunger being adapted to extrude measured droplets of cement through said nozzle and upon a lens held by said holder, and a heating element extending about said orifice and out of contact therewith for maintaining said droplets of cement issuing from the nozzle at a temperature facilitating dropping.

2. A machine for applying metered quantities of cement to lenses comprising a support, a cement cylinder mounted above the lens holder, means for heating the cylinder, a plunger movably mounted in the cylinder, a pawl and ratchet for advancing the plunger into the cylinder by predetermined amounts, a nozzle carried by the cylinder for directing cement to a lens carried by the lens holder, a heating element outside of and extending below the apertureof the nozzle to heat a droplet issuing therefrom to a dropping temperature, and means for determining the stroke of the pawl and ratchet mechanism whereby at each movement thereof a definite quantity of cement may be delivered upon a lens resting on said lens holder.

3. A machine for applying metered quantities -of cement to lenses comprising a support, a lens holder mounted thereon,` a cement cylinder mounted above the lens holder, means for heating the cylinder, a plunger movably mounted in the cylinder, a pawl and ratchet for advancing the plunger into the cylinder by predetermined amounts, a nozzle carried by the cylinder for directing cement to a lens carried by the lens holder, a heating element outside of and extending below the aperture of the nozzle to heat a droplet issuing therefrom to a dropping temperature, and means for determining the stroke of the pawl and ratchet mechanism whereby at each movement thereof a definite quantity of cement may be delivered upon a lens resting on said lens holder, and means for heating a lens carried by said holder.

A 4,. A machine for applying metered quantites o'f cement to lenses comprising a support, a lens holder mounted thereon, a cement cylinder mounted above the lens holder, means for heating the cylinder, a plunger movably mounted in the cylinder, a pawl and ratchet for advancing the plunger into the cylinder by predetermined amounts, a nozzle carried by the cylinder for directing cement to a lens carried by the lens holder, a heating element outside of and extending below the aperture of the nozzle to heat a droplet issuing therefrom to a dropping temperature, and means for determining the stroke of the pawl and ratchet mechanism whereby at each movement thereof a definite quantity of cement may be delivered upon a lens resting on said lens holder, means for heating a lens carried by said holder, said cylinder heating means, said droplet heating means and said lens heating means all including a variable heat adjusting member whereby predetermined relative temperatures of the heating means may be obtained and droplets of cement may be deposited on a lens in the lens holder.

5. A machine for applying metered quantities of cement to lenses comprising a support, a lens holder slidably mounted thereon, a cement cylinder mounted above the lens holder, a plunger movably mounted in the cylinder for advancement by predetermined amounts, a nozzle carried by the cylinder for directing cement to a lens carried by the lens holder, a heating element below and positioned substantially axially of the nozzle for heating a droplet issuing therefrom, said lens holder including a mount for lenses movable with the lens holder on the suppgrtlfor.V

positioning a lens held by the mount beneath the droplet nozzle.

WILLIAM T. SHERWOOD. 

